1. Field of the Invention
The invention relates generally to integrated circuits and more specifically to methods and structures for temperature self-monitoring within integrated circuits.
2. Discussion of Related Art
Integrated circuits (“ICs”) are electronic devices that integrate, within a single package, a significant number and variety of lower level, discrete electronic components and circuits. Common examples of such an integrated circuits are the devices within typical consumer electronic products including, for example, cellular telephones, personal digital assistants (“PDA”), personal computers, etc. By so integrating a significant number of discrete electronic components and circuits within an integrated circuit package, manufacturers can dramatically reduce costs associated with manufacturing. In addition, by more tightly coupling discrete components in a smaller space, signals exchanged between various components may do so at faster speeds and with reduced loss of signal amplitude and quality.
It is common for modem integrated circuits to integrate millions or even tens of millions of discrete electronic circuits and components within a single integrated circuit package. Enhanced functionality within a single integrated circuit package is one of the factors that contribute to the size of such an integrated circuit as measured by the number of discrete components within. It is common that the components within an integrated circuit package operate in synchronicity with one or more supplied clock signals. The frequency of the clock signals is typically one important measure of the performance of a particular integrated circuit. For example, a general-purpose microprocessor integrated circuit (CPU) may enhance its performance by increasing the frequency of the clock applied thereto.
All electronic circuits generate some amount of heat in their operation. Design and manufacturing processes may help reduce energy lost in the form of heat energy, however it remains axiomatic that operating electronic circuits will continue to generate heat. As the density of discrete components integrated within a single integrated circuit package rises, the heat generated within such a package may increase dramatically. Examples of very high density integrated circuits are the circuits presently referred to as “System On a Chip” or “SOC.” A SOC contains in a single integrated circuit common in, for example, present day personal computers. For example, such a SOC may include a CPU, a memory controller and direct memory access controller (“DMAC”), a PCI bus interface component or other peripheral I/O interface buses, graphics controller, etc. Such a highly integrated circuit can dramatically reduce the manufacturing cost of present day personal computers and other consumer electronic products. However, such high component density increases problems of heat generation and dissipation.
Furthermore, in addition to circuit density as a factor in heat generation, clock frequency of the clock signals supplied to such integrated circuits is another contributing factor to generation of heat. In other words, the faster electronic circuits operate, in general, the more heat generated by operation of that circuit. Processor clock speed of present day personal computers continues to push the limits of present technology and heat generation and dissipation.
Therefore, as can be seen, enhanced functionality and increased clock speed of present-day integrated circuits gives rise to a significant problem in that operating integrated circuits must be kept within desirable operating temperature ranges to avoid damage to the integrated circuit—damage even to the extent of partial or total failure thereof.
As the complexity and corresponding heat generation of modem integrated circuits has risen, electronic designers often include temperature monitoring and cooling elements within electronic product designs. For example, personal computer users are familiar with the constant hum of fans used to exhaust excess heat from an operating personal computer. Where electronic products are intended for portable use it is problematic to constantly operate fans or other cooling devices because operation of such fans consumes valuable energy from the batteries of the portable device. It is therefore common in present day electronic product designs to include temperature monitoring features so that cooling devices such as fans can be intelligently controlled to preserve precious battery life in, for example, portable electronic products.
Temperature monitoring circuit designs add complexity and hence associated cost to electronic products. In typical systems such monitoring circuits are external to the integrated circuits and monitor internal ambient air temperature surrounding integrated circuits that are particularly sensitive to overheating. Such extra circuits may include a thermocouple, or other temperature transducing devices, as well as analog to digital conversion electronics for converting the analog signal generated from such a temperature sensor into an appropriate digital signal for further processing. The digital signal may then be processed in accordance with desired logic to produce appropriate control signals for management of cooling apparatus such as fans or other active cooling devices.
As can be seen from the above discussion, it remains an ongoing problem to reduce cost and complexity associated with temperature monitoring of complex integrated circuits to permit intelligent management of cooling devices within electronic products. In particular it remains a problem to monitor temperature to permit intelligent temperature controls in portable electronic products dependent on precious battery power.